Siemens GIGASET C475 IP - Manual (Page 142)

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Web configurator – configuring the telephone via a PC
Optimising voice quality for VoIP connections
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Optimising voice quality for VoIP connections
You can make general and connection-specific settings to improve the voice quality for
VoIP telephony.
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Open the following Web page: Settings
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Telephony
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Audio .
The voice quality for VoIP connections is mainly determined by the voice codec used for
transferring the data and the available bandwidth of your DSL connection.
In the case of the voice codec, the voice data is digitalised (coded / decoded) and com-
pressed. A "better" codec (better voice quality) means more data needs to be transferred,
i.e. perfect voice data transfer requires a DSL connection with a larger bandwidth.
The following voice codecs are supported by your phone:
G.722
If you register an HDSP capable handset (HDSP= High Definition Sound Performance)
with your base station, the calls you make using the handset via G.722 VoIP connections
will have a fantastic sound quality. Gigaset handsets S67H and SL37H, for e.g., are HDSP
capable.
The broadband speech codec
G.722 works at the same bit rate as G.711 (64 kbit/s per
speech connection) but with a higher sampling rate.
G.711 a law / G.711 µ law
Excellent voice quality (comparable with ISDN). The necessary bandwidth is 64 kbit/s
per voice connection.
G.726
Good voice quality (inferior to that with G.711 but better than with G.729).
Your phone supports G.726 with a transmission rate of 32 kbit/s per voice connection.
G.729
Average voice quality. The necessary bandwidth is less than 8 kbit/s per voice connec-
tion.
Both sides of a phone connection (caller/sender side and receiver side) must use the same
voice codec. The voice codec is negotiated between the sender and the recipient when
establishing a connection.
You can influence the voice quality by selecting (bearing in mind the bandwidth of your
DSL connection) the voice codecs your phone is to use, and specifying the order in which
the codecs are to be suggested when a VoIP connection is established.
Area: Settings for Bandwidth
The settings in this area influence all VoIP connections (VoIP phone numbers).
Allow 1 VoIP call only
Generally speaking you can make two VoIP calls at the same time on your phone. If,
however, your DSL connection has a narrow bandwidth, there may be problems if two
VoIP calls are made at the same time. The data is no longer transferred properly (long
voice delay, data losses etc.).
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Activate Yes next to Allow 1 VoIP call only to prevent any further parallel VoIP phone
connections being established.
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If you wish to permit two VoIP connections, activate the No option.